In a wireless communication system adapted to an LTE (Long Term Evolution) scheme or the like, of which specifications have been developed in 3GPP (3rd Generation Partnership Project), a wireless terminal transmits a reference signal to a wireless base station. The wireless base station estimates a state of a transmission path based on the received reference signal and forms antenna directivity for downlink user data.
As a method of transmitting a reference signal, such a method that a wireless terminal transmits an SRS (Sounding Reference Signal) by using a part of an UpPTS (uplink part) in a switch subframe or a part of an uplink subframe (for example, a last symbol) has been known (see, for example, Japanese Patent Laying-Open No. 2010-28192 (PTL 1)).